Abstract:
Ti-rich double perovskites LnCu(3-y)Ti(2-x)Mn(2+x+y)O(12) have been synthesized at normal pressure, with a wide homogeneity range, 0 < x < 0.5 and 0 < y <= 1. ALL these oxides are ferrimagnetic, with T-C ranging from 160 K to 293 K, in spite of the high 3d(0)-Ti content in the octahedral sites. The evolution of T-C can be monitored on the basis of three factors-antiferromagnetic superexchange interactions Cu2+up arrow-O-Mn3+/4+down arrow-O-Cu2+up arrow, double exchange Mn4+-O-Mn3+ interactions in the octahedral sites and chemical pressure due to the size effect of Ln(3+). Differently from high pressure synthesized manganites, these oxides exhibit maximum magnetoresistance at T-C, similar to single perovskite manganites. Intrinsic magnetoresistance can thus be obtained at room temperature, but with a smaller amplitude compared to single manganites, due to the dilution effect of titanium.
